Borehole inclinometer



y 29, 1956 A. B. HILDEBRANDT ET AL BOREI-IOLD INCLINOMETER Filed May 26, 1953 DRILL STRING BORE2 HOLE NON MAGNETIC MATERIAL TO ATTACH ABOVE BIT MUD 5BY-PASS UPPER BELLOWS RING SEAL I8 PISTON CHAMBER PISTON FOR LOOKING PENDULUM I6 wars 3 LASS COMPASS INDEX READING ARM 39 RING SEAL l8 COMPASS l2 IOCK ING PISTON COMPREESION SPRING DRILL STRING OR BIT ALEXANDER B.HILDEBRANDT INVENTOR FREDERIC H. DEILY United States Patent BoREnoL-E rNCtmoMnrEa Alexander. B. Hildebrandt and Fredric Daily, Tulsa,

Okla, assignors to Esso Research and Engineering Company, a corporation of Delaware Application May-26, 1953, Serial No. 357,538

3 Claims. (Ci; 33*20'5) The present invention is concerned with the logging of bore holes being drilled for the production of oil. The invention is moreparticularlyconcerned with an apparatus whichis' adapted to be attached to the drill pipe or: drill stem-while drilling and whichwill give a. complete bore hole inclination plot without the necessity'of removing the:string and thereafter determining the inclination of the bore hole by special down hole equipment.

It is well known in the art to drillboreholes inthe earths substrata in order to search'for and to'produce oil. In these operations the bore hole is'usually bored by utilizing a drill string having attached'toits lower end thereof various types of drill bits. During thedrilling operation drilling fluid or mud is. passed downwardly within .the drill string and upwardly in the area between the bore hole and the drillstringinorder to remove the drillYcuttings. During thedrilling operation it is essential that acompleteborehole inclination 'plot be known in order to determine the actual depth of the bore hole and the extent anddirection of deviation from the vertical. Heretofore in the past it has been necessary to remove the drill string section by section and then to pass downwardly" in the bore hole special instruments adapted to give the inclination plot of the bore hole. After this has been determinedthe drill string is assembled section by section and the drilling operation continued.

By the apparatus of the present invention the necessity for lowering a special instrument and withdrawal of that instrument from the bore hole is eliminated. The apparatus is attached to the drill pipe but does not interfere with normal drilling operations. When the drill pipe is withdrawn from the bore hole during the normal course of drilling operations, as for example to change drill bits, the bore hole inclination and orientation can be noted Without incurring the loss of time that would be involved in making a trip into and out of the bore hole with a special logging tool.

The apparatus of the present invention may be fully understood by reference to the attached drawing illustrating one embodiment of the same. The apparatus is shown attached to the lower end of a drill string 1 positioned within bore hole 2. The apparatus of the present invention comprises an elongated casing 4 having a diameter substantially equivalent to the diameter of the drill string or drill collars, and adapted to be attached to the loWer end of the drill string and adapted to have attached to its lower end a suitable bit or further sections of drill pipe or drill collars, the upper end of whichever element is used being designated by reference numeral 3. A drilling mud by-pass 5 communicates between the entrance passage 6 and the exit passage 7 of the inclinometer assembly. An upper bellows chamber 8 full of drilling fluid communicates freely with entrance passage 6 by means of port 9. This upper bellows chamber 8 contains upper bellows element 10 which is full of liquid, preferably a selected clear oil. A lower bellows chamber ll is full of drilling fluid and communicates freely with exit passage-7 bymeansof port 12. Lowerbellowschamberll 'containslower bellows 13 which bellows is fullof the-:selected oil. A free-swinging pendulum 14 is posi-' tioned within piston chamber 15. Piston 16 is slidably positioned within piston chamber 15. The downward movement of'piston 16is restricted by stop 17 while the upper movement is restricted by the lower point of pendulum 14. A suitable ring seal 18 is used'to preventthe how of oil to within the piston. The piston is suitably graduated, as bymeans of the scale so as to determine the exact position of the pendulum 14upon locking. Free communication isprovided-f'rom within upper bellows 10 to the area within piston chamber 15 by means of ports 38 A compass 20 is disposedabove an inverted compass locking piston 21. An ind'ex reading arm 39 extends over thefaceof the compassso as to facilitate an exact determination of the compass position; Acompression spring 22-maintains an 'upward thrust against the head of piston 21. The area between the head of piston 16 and the baseot piston 21 is'filled with a clear oil so that the readings-of the pendulum and the compasscan' readily be determined'by mirror elements 32.

In operation the inclination assembly functions as'fOllows. Drilling mud ispumped 'down the drill string 1 through entrance passage 6, through-mudby-pass send out exitpassage-7 into the drill'bit ora lower section of drilla' string. The mud flows through the bit an'd returns to the surface throughthe annulus betw'eenthe drill string and'the bore hole. The pressure, and therefore the force that actuates the piston system is provided bythe slight resistance to the flow 'ofiered by mud by-passS: When normal drilling fluid flow is maintained through the drill string" a small pressure drop-or APexists'between the entrance passage 6-" andthe exit passage 7. This pressure; difle'rential'is sufiicient to actuate the bellows 'of'the instrument. The fluid .ports 9 and .12 transmit the'average fluid'pressure drop that occurs through theinstrument while serving, because of their restrictedsi-ze, to damp outerratic fluid pressure surges. Thus when drilling mud is being circulated, a downward thrust is exerted on upp'er bellows 10 throughport 9. Compression of bellows loforces liquid through ports 3S -against piston 16. Downward motion of piston 16 forces the liquid below it through ports 25, moving piston 21 down against the upward thrust of spring 22. Note here that the strength of spring 22 may be increased such that under normal circulating rates the pressure drop through mud by-pass 5 is not sufiicient to release the compass and pendulum. Therefore, in this modification the assembly will not be free during drilling and not subject to drilling vibrations. When a reading is desired, the circulating rate is increased, causing the pressure drop across the mud by-pass 5 to increase, which in turn causes the compass and pendulum to be freed during the time the mud is circulated at an increased rate. An increased circulating rate for a period of one to three minutes should be sufficient to allow the compass and pendulum to come to equilibrium. Flow is then stopped, causing the compass and pendulum to be locked and the instrument is then removed from the bore hole.

When piston 21 moves downward against the upper thrust of compression spring 22, the fluid below the head of piston 21 flows into lower bellows 13 through ports 27 and an equilibrium is obtained. However when pumping is stopped for the removal of the drill string the upper thrust of spring 22 pushes piston 21 upwardly and locks compass 20 in place. When piston 21 moves upwardly it pushes the fluid above it against piston 16, causing the latter to move upwardly and lock pendulum 14 in place. The instrument is then withdrawn to the surface upon withdrawal of the drill string from the bore hole and the position of compass 21 and pendulum 14 are determined. This is accomplished by removing a removable plug 30 and looking through a glass 31 and taking the readings from mirrors 32. The head of piston element 16 is transparent so that the position of the point of pendulum 14 on scale 40 is readily determined.

A particular adaptation of the present invention is to select the strength of spring element 22 so that the AP across the unit at normal pumping rates is insuflicient to force the spring downwardly. Thus the pendulum and the compass will not be released. For example, normal pumping rates in gallons per minute vary in the range of from about 100 to 500 gallons per minute, usually in the range of about 200 to 300 gallons per minute. In accordance with a preferred concept of the present invention spring element 22 exerts suflicient upward thrust against the pressure differential secured during these pumping rates so as to overcome the AP keeping the respective pistons in the upward position. Thus the pendulum and compass elements will not be released. A normal drilling operation can be carried out at these rates. However when it has been decided to withdraw the drill string and it is desired to know the inclination of the bore hole the pumping rates will be increased about, for example, from five hundred gallons per minute, say to seven hundred gallons per minute. The increased AP resulting from this increase across the assembly will overcome the upward thrust of the spring, piston 16 and piston 21 will be forced downwardly and the pendulum and compass elements Will swing free. Their position will be determined by the inclination of the bore hole and the orientation of the assembly. Pumping can then be stopped, the AP will drop to zero and the spring elements will exert the upward thrust and force piston 21 and 16 upwardly thus locking the pendulum and the compass in the position assumed while swinging freely.

Having described the invention, it is claimed:

1. Improved bore hole inclinometer assembly adapted for insertion in a string of drill pipe above a drill bit in a bore hole, comprising: an elongated casing member attachable to said drill string and having a top central opening and a bottom central opening communicating with the bore of the drill string, an upper bellows chamber positioned Within said casing member, an upper bellows within said upper chamber, a piston chamber positioned below said upper bellows chamber, in fluid communication with the interior of said upper bellows, a lower bellows chamber positioned below said piston chamber, a lower bellows positioned within said lower bellows chamber with the interior of said lower bellows in fluid communication with said piston chamber, a pendulum suspended within said piston chamber, a first piston slidably positioned within said piston chamber adapted to move into contact with and thereby lock said pendulum, a compass mounted within said piston chamber, a second piston slidably positioned within said piston chamber adapted to move into contact with and thereby lock said compass, a spring urging at least one of said pistons into locking position, fluid filling said piston chamber and said bellows, means establishing fluid communication between said upper bellows chamber and said top central opening, means establishing fluid communication between said lower bellows chamber and said bottom central opening, and a channel within said casing connecting said top central opening with said bottom central opening, said channel presenting greater resistance to fluid flow than said top and bottom central openings, whereby fluid circulation through said drill string will exert a pressure differential, communicable to said pistons through said bellows, suflicient to move said pistons out of locking position against the action of said spring.

2. Apparatus as defined by claim 1 including a fluidsealed inspection port whereby the positions of said compass and of said pendulum can be determined by visual inspection external of said piston chamber.

3. Apparatus as defined by claim 2 including mirror elements positioned within said piston chamber adjacent said pendulum and said compass and visually accessible through said inspection port whereby to facilitate visual inspection of said pendulum and said compass.

References Cited in the file of this patent UNITED STATES PATENTS 1,895,615 Elliott Jan. 31, 1933 1,935,078 Cavins Nov. 14, 1933 2,486,529 Jackson Nov. 1, 1949 FOREIGN PATENTS 168,596 Germany Feb. 24, 1906 10,764 Great Britain 1906 

1. IMPROVED BORE HOLE INCLINOMETER ASSEMBLY ADAPTED FOR INSERTION IN A STRING OF DRILL PIPE ABOVE A DRILL BIT IN A BORE HOLE, COMPRISING: AN ELONGATED CASING MEMBER ATTACHABLE TO SAID DRILL STRING AND HAVING A TOP CENTRAL OPENING AND A BOTTOM CENTRAL OPENING COMMUNICATING WITH THE BORE OF THE DRILL STRING, AN UPPER BELLOWS CHAMBER POSITIONED WITHIN SAID CASING MEMBER, AN UPPER BELLOWS WITHIN SAID UPPER CHAMBER, A PISTON CHAMBER POSITIONED BELOW SAID UPPER BELLOWS CHAMBER, IN FLUID COMMUNICATION WITH THE INTERIOR OF SAID UPPER BELLOWS, A LOWER BELLOWS CHAMBER POSITIONED BELOW SAID POSITION CHAMBER, A LOWER BELLOWS POSITIONED WITHIN SAID LOWER BELLOWS CHAMBER WITH THE INTERIOR OF SAID LOWER BELLOWS IN FLUID COMMUNICATION WITH SAID PISTON CHAMBER, A PENDULUM SUSPENDED WITHIN SAID PISTON CHAMBER, A FIRST PISTON SLIDABLY POSITIONED WITHIN SAID PISTON CHAMBER ADAPTED TO MOVE INTO CONTACT WITH AND THEREBY LOCK SAID PENDULUM, A COMPASS MOUNTED WITHIN SAID PISTON CHAMBER, A SECOND PISTON SLIDABLY POSITIONED WITHIN SAID PISTON CHAMBER ADAPTED TO MOVE INTO CONTACT WITH AND THEREBY LOCK SAID COMPASS, A SPRING URGING AT LEAST ONE OF SAID PISTONS INTO LOCKING POSITION, FLUID FILLING SAID PISTON CHAMBER AND SAID BELLOWS, MEANS ESTABLISHING FLUID COMMUNICATION BETWEEN SAID UPPER BELLOWS CHAMBER AND SAID TOP CENTRAL OPENING, MEANS ESTABLISHING FLUID COMMUNICATION BETWEEN SAID LOWER BELLOWS CHAMBER AND SAID BOTTOM CENTRAL OPENING, AND A CHANNEL WITHIN SAID CASING CONNECTING SAID TOP CENTRAL OPENING WITH SAID BOTTOM CENTRAL OPENING, SAID CHANNEL BOTTOM CENTRAL OPENINGS, WHEREBY FLUID CIRCULATION THROUGH SAID DRILL STRING WILL EXERT A PRESSURE DIFFERENTIAL, COMMUNICABLE TO SAID PISTONS THROUGH SAID BELLOWS, SUFFICIENT TO MOVE SAID PISTONS OUT OF LOCKING POSITION AGAINST THE ACTION OF SAID SPRING. 